Published August 17, 2021 © GPL3+

Daylight-detecting Outdoor Light

This circuit turns a light on or off depending on how bright its surroundings are. This can be used as a daylight-sensitive outdoor light.

BeginnerShowcase (no instructions)1,287

Things used in this project

Hardware components

Arduino UNO

Jumper wires (generic)

Male/Female Jumper Wires

Switch Actuator, APEM A01 series Illuminated Push-Button Switches

Any button is good, you don't need something like this.

LED (generic)

Resistor 1k ohm

Relay Module (Generic)

Make sure it supports 240V AC, or it will likely fry.

9V DC Power Supply for Motherboard

If you are using multiple relays, you should use a 12V power supply instead.

LED Light Bulb, Frosted GLS

I couldn't find a listing for the one I used. It is simply a lightbulb that can be connected to an AC wall socket for power. This allows me to cut a portion of the wire so I can connect it to the relay.

Power splitter to multiple AC outlets

It only needs 2 outlets, unless you are using more lights.

Photo resistor

Software apps and online services

Arduino IDE

Story

This is my second Arduino Project. It is a powerful light that turns on or off depending on the brightness of its surroundings. It also has a manual mode, allowing you to manually toggle the light.

If you build an enclosure for it and calibrate the photocell, this can be used as an outdoor light, which turns off during the day, when it is unnecessary, and turns on at night. For power, this exact circuit only requires one AC wall socket.

I did not complete the process to utilize this practically since school is starting soon for me, and I already had a more robust commercial product with the same functionality lying around.

Assuming you are using a generic AC-powered light, like I did, you need to cut one side of its wire (as can be seen in the picture) and remove some insulation so you can plug it into the relay. If you are planning on using this practically, you will likely use a different lighting configuration (e.g. a more power-consuming light, mutiple lights, etc.). For this, you may need to use multiple AC wall sockets. For each extra wall socket, you will need to use another relay. Simply copy the code for one relay and paste it right next to it.

Code

Photocell Project Code

#define photoresistor 0
#define MorA 8
#define modeBtn 4
#define toggleBtn 5
#define led 2

int mode = 0; // 0 is Auto, 1 is Manual
int on = 1;

void setup() {
  pinMode(modeBtn, INPUT_PULLUP);
  pinMode(toggleBtn, INPUT_PULLUP);
  pinMode(led, OUTPUT);
  pinMode(MorA, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  int light = analogRead(photoresistor);
  
  if (digitalRead(modeBtn) == LOW){
    mode += 1;
    mode = mode % 2;
    if (mode == 0){
      Serial.println("Auto");
      digitalWrite(MorA, LOW);
    }
    if (mode == 1){
      Serial.println("Manual");
      analogWrite(MorA, 150);
    }
    delay(1000);
  }

  if (mode == 0) {
    if (light < 300) {
      digitalWrite(led, LOW);
    }
    else {
      digitalWrite(led, HIGH);
    }  
  }

  if (mode == 1) {
    if (digitalRead(toggleBtn) == LOW){
      on += 1;
      on = on % 2;
      if (on == 0){
        Serial.println("OFF");
        digitalWrite(led, HIGH);
      }
      if (on == 1){
        Serial.println("ON");
        digitalWrite(led, LOW);
      }
      delay(1000);
    }
  }
}